The present invention is directed to an internal wrench-adapter for rotating a plug of a housing for an oil filter. In some later-model vehicles, an oil filter is housed in a separate housing or casing, which casing has a closure cap or plug that is screwed onto the casing. This type is typically called an "in-the-pan" cannister oil filter. When it is desired to replace the oil filter, the plug is unscrewed from the casing, and a new oil filter inserted. Thereafter, the plug is screwed back on. The plug is conventionally rotated by gripping with a conventional wrench or pliers the hexagonally-shaped projection on the exterior surface of the plug. However, since the hexagonal-shaped projection projects from a recessed surface face of the plug, the projection is hard to grip and, over time, becomes worn and misshapen, making it even more difficult for a conventional hex-head wrench or tool to grip and turn it.
Internal wrenches are well-known. One such wrench is shown in U.S. Pat. No. 2,800,043--Young, in which three, arcuately spaced-apart, pivotal jaw-members are rotated in one direction or the other for gripping an internal diameter tube via an inner rotatable actuator. Initial rotation of the inner rotatable actuator causes the jaws to first rotate in a respective direction until they frictionally engage the internal diameter. Further rotation is then translated into rotation of the tube itself, whereby the greater torque applied to the actuator, the greater frictional engagement of the jaw-members with the internal diameter of the tube. The present invention has adapted such an internal wrench to the specific case of the "in-the-pan" cannister oil plug.